Just to be excruciatingly clear: both configurations are running the same underlying Emacs version, and both are using daemon+emacsclient. The only difference is the configs, i.e., the runtime ~/.emacs.d/.

Old'n'crufty config works as expected: particularly, the spew in the console in which I run my startup scriptlet ends with

failed options

deprecated options

Recompiling Emacs with debug symbols. That seems like a lot of work.

Bisecting config. This is unnecessary, because I've been porting function from old'n'crufty config to Prelude-based config step-by-step, and I know exactly what is failing: it's loading my old desktop. What I want to investigate is,